1. Field of the Invention
The present invention relates to a load port for opening and closing a door of a wafer carrier, a wafer processing apparatus, and a method of replacing atmosphere.
2. Description of the Background Art
Heretofore, a wafer carrier has been used as a container for holding wafers in a manufacturing process of semiconductor devices.
FIG. 9 is a perspective view illustrating a known wafer carrier of side-door integrated type. FIG. 10 is a perspective view showing an inside of a carrier door 20 of the wafer carrier 100 shown in FIG. 9.
Wafer carriers as shown in FIG. 9 include, for example, a wafer carrier shown in a catalog made by FLUOROWARE company. This type of wafer carrier is referred to as FOUP in the SEMI Standards. FOUP is the abbreviation of a xe2x80x9cfront opening unified pod.xe2x80x9d Detailed information, such as dimensions, is described in the SEMI Standards E 52, E 1.9, or E 47.1.
In FIGS. 9 and 10, reference numeral 100 denotes a wafer carrier used as a container for holding wafers, 10 denotes a carrier shell, 12 denotes a robot flange, 13 denotes a manual handle, and 14 denotes a side rail. Reference numeral 20 denotes a carrier door, 21 denotes a sealing member (packing), 22 denotes a retainer for holding wafers, 23 denotes an engaging piece of a door-clamping mechanism (stopper mechanism) for engaging to the carrier shell 10, 24 denotes a registration-pin hole, and 25 denotes a latchkey hole. Although not shown in the drawings, inside the carrier shell 10 are formed wafer teeth for seating wafers, holes corresponding to the engaging piece 23 of the door-clamping mechanism of the carrier door 20, thick portions, and sealing portions or the like.
As FIG. 9 shows, the wafer carrier 100 includes the carrier shell 10 and the carrier door 20. The carrier shell 10 is a housing having an open face in one surface, and the carrier door 20 fits to the carrier shell 10 at this open face. In the state where the carrier door 20 fits to the carrier shell 10, that is, in the state where the carrier door 20 is closed, the wafer carrier 100 is in a sealed state.
As shown in FIG. 10, inside the carrier door 20, a sealing member 21 is provided on the portion contacting the carrier shell 10. This is used for maintaining the air-tightness of the wafer carrier 100.
Unlike an open cassette (SEMI Standards E 1.9 and others, before 8-inch wafers), the wafer carrier 100 protects wafers from foreign matter in the air and chemical contamination by holding substrates to be processed (hereafter referred to as xe2x80x9cwaferxe2x80x9d) in a sealed space.
On the other hand, in order to stop the above-described wafer carrier 100 at a wafer processing apparatus (semiconductor manufacturing apparatus), and to open and close the carrier door 20 to load and unload wafers, a load port having an FIMS face specified in the SEMI Standards is required. FIMS is an abbreviation of xe2x80x9cfront-opening interface mechanical standardxe2x80x9d.
FIG. 11 is a sectional view for illustrating a conventional wafer processing apparatus comprising a load port.
As FIG. 11 shows, the load port 300 comprises a wall surface (body surface) for separating the mini-environment 40 in the wafer processing apparatus 200 from the exterior; a kinematic pin 31 used for aligning the wafer carrier 100 on an installation table 30; and a load port door (FIMS door) 32 fitted to the carrier door 20, and taken in the mini-environment 40 in the wafer processing apparatus 200 together with the carrier door 20 after the opening operation of the doors. Among the wall surfaces of the wafer processing apparatus 200, a surface contacting a sealing surface (FOUP sealing surface) 26 of the carrier shell 10 and maintaining air-tightness is called an FIMS sealing surface 27.
The wafer processing apparatus 200 also comprises a wafer-transferring robot 41, and an FFU (fan filter unit) 42 for cleaning the air in the mini-environment 40.
The sealed-type wafer carriers 100, such as FOUP, are generally formed of a high-performance plastic material. However, since plastic materials have a property to permeate moisture or the like, moisture or the like may enter inside the wafer carrier 100. In addition, outside air may permeate into the wafer carrier 100 through the sealing material 21 due to the mechanism of molecular diffusion or the like.
Therefore, the humidity, oxygen content, or the like tend to increase with the lapse of time.
Also, when wafers whereto a photoresist is applied are stocked in a wafer carrier 100, the organic solvent vaporized from the photoresist applied to the wafers may adhere to the internal wall of the wafer carrier 100. In this case, even after the wafers are removed, the organic solvent adhered to the internal wall of the wafer carrier 100 may remain intact. Thereafter, by the re-vaporization of the organic solvent, the atmosphere inside the wafer carrier 100 may be contaminated by organic compounds.
As a measure against such elevations of humidity and oxygen content, and organic contamination in a wafer carrier 100, there has been proposed a method to introduce N2 or dry air from the bottom of the wafer carrier 100 in the state where the carrier door 20 is closed to replace the atmosphere inside the wafer carrier 100.
However, as FIG. 11 shows, a plurality of wafers 16 are horizontally accommodated in the wafer carrier 100. Therefore, there has been a problem that wafers or the like accommodated in the wafer carrier 100 interfere with N2 gas or the dry air to replace the atmosphere inside the wafer carrier 100.
As described above, even if the airtight wafer carrier 100 is used, there has been a problem that outside air or moisture or the like permeates due to the characteristics of plastics or rubber, and humidity or oxygen content inside the wafer carrier 100 may increase. Also, by accommodating wafers 16 whereto a photoresist is applied are accommodated, the atmosphere inside the wafer carrier 100 may be contaminated by organic compounds.
Even if N2 gas or dry air is simply introduced into the wafer carrier 100, obstructs in the wafer carrier 100, such as wafers 16, make it difficult to replace the atmosphere inside the wafer carrier 100 with a clean gas in a short time.
However, the elevation of humidity or oxygen content in the wafer carrier 100, or organic contamination of the wafer carrier 100 raises problems of the growth of native oxide films, and poor withstand voltage of the gate.
The present invention has been conceived to solve the previously-mentioned problems and aims at providing a load port, a wafer processing apparatus, and a method of replacing gas that can replace the atmosphere inside the wafer carrier efficiently in a short time.
The above objects of the present invention are attained by a following load port, by a following wafer processing apparatus and by a following method of replacing atmosphere.
According to a first aspect of the present invention, the load port for placing a wafer carrier thereon comprises a first door for opening and closing a carrier door constituting a face of the wafer carrier. An atmosphere replacing mechanism purges atmosphere inside the wafer carrier through an open face of the wafer carrier in the state where the carrier door is open.
According to a second aspect of the present invention, the wafer processing apparatus having a load port for placing a wafer carrier thereon comprises a first door for opening and closing a carrier door constituting a face of the wafer carrier. An atmosphere replacing mechanism purges the atmosphere inside the wafer carrier through an open face of the wafer carrier in the state where the carrier door is open.
According to a third aspect of the present invention, in the method of replacing atmosphere by purging the atmosphere inside a wafer carrier placed on a load port of a wafer processing apparatus, the atmosphere inside the wafer carrier is purged, after transferring wafers after predetermined processing, through an open face of the wafer carrier in the state where the carrier door is open.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.